Where is the best thread making video featuring correct method?

[lander (CAD CAM CNC)]

@Anthony_Yan

Don’t know if this would help, but I made a thread-generator in Grasshopper. You can find it here:

Here is a helical thread-generator I’ve been working on. Mostly intended to generate custom-threads for 3d-printing. However, it might be useful for other people. Despite the “simplicity” of helical threads, getting everything together turned out to be much more work than I expected. Especially when allowing for tapered threads. Please have a look, and let me know if anything breaks, or how to improve this Grasshopper script. I’m using this project to learn Grasshopper as well as make some…

Yes, I gave you props on this in another permutation of this same subject matter about 20 days prior:

How to model a nut no videos anywhere

This person looks like they’re keeping their tool up to date: But looks pretty complicated I kinda suspected that “boltgen” was falling behind on updates/development: And not sure why everyone thinks ‘Mcmastercarr’ has the best most accurate 3D modelers on the planet that make perfect threads on every part you can download. This used to not be the case. I’ve seen some pretty bad files I’ve downloaded from them. I always just consider it as “mockup” geometry when I’m lazy …

@Anthony_Yan

@Helvetosaur

If you use Sweep1 on a helix with a planar profile in the plane of the rotation axis of the cylinder being cut and you then take a section through the cut part in that plane, you will get perfect V shapes that are the same as the cutting profile.

This is correct for straight threads. However, it will not be correct for a tapered thread. Mathematically, you will find a deviation if you try to do it on say, 1/4" NPT tapered threads.

What I meant to say, is that in general, Sweep1 and Sweep2 cannot generate tapered threads that are mathematically correct.

Geometrically, this is interesting. So I can generate some example files, if you want to discuss further.

I don’t see what tapered vs straight would be any different relative to what’s possible. I look forward to studying your examples, as I remain skeptical.

@Anthony_Yan

Okay, it sounds like there is enough interest in why Sweep1 and Sweep2 fail on tapered threads. I will make some example files to demonstrate this. I’ll put in in a separate thread, and point to it when ready.

Please note that Sweep1 and Sweep2 will work on straight threads.

(NOTE: If this isn’t obvious to you, don’t worry, I got it wrong too. It was only after struggling to create my first tapered thread, did I realize what was wrong.)

I look forward to it.

@Anthony_Yan

So these bolts look like they were formed by thread-rolling. Most mass-produced bolts are done by some form of thread-rolling, and are not machined.

Indeed that seems to be the case in common scenarios, yet thread-rolling is probably done by machines, hence they’re machined.

@Anthony_Yan

In thread-rolling, a cylindrical blank (possibly with conical reliefs and/or chamfers) squeezed against a die, and the threads are created by cold-forming. In thread-rolling, sometimes the dies are round with helical threads. Other times the dies are flat and “unrolled” versions of the round dies. They’re flat, with straight (but slightly diagonal) grooves cut into them. The blank rolls across the die, and the straight groves (cold) form the threads.

I can also use a ‘form tap’ with ‘roll forming geometry’, on a CNC milling machine to machine threads.

@Anthony_Yan

Not sure how to model this in CAD, because the thread-rolling process actually pushes metal away from the valleys and towards the peaks. The circled red area is where the die starts to slowly engage the blank (the peaks of the die here are more shallow). I think the bolt blank has a conical taper in this region that expands from the pitch-diameter to the full-diameter of the unthreaded part.

Yes, because the grain and molecules of thread forming machining operations transforms the material differently than cutting does, then you’d have to model the geometry accordingly. It’s merely just a different profile. I could demonstrate it if there’s no links here yet.

@Anthony_Yan

P.S. I admit to having watched too many episodes of How It’s Made (Discovery Channel). Most, if not all the episodes are on YouTube these days (unofficially).

That’s awesome. I really like that show. I appreciate the links.

@Anthony_Yan

(1) Telling beginners to “just read the manual” (RTFM) or “lemme google that for you” (LMGTF) is not helpful, and is common problem in toxic online communities. If that is your gut-reaction (which can be legit), then just don’t reply. Let others answer.

Maybe I’m the one guilty of that for throwing a few rough jabs. Yeah I was probably having a bad day at first, but hope I was still somewhat friendly, and I’m sorry for those actions, but I’m better now.

I guess I lost some tolerance recentlyt, and I remain skeptical that a member of about 10yrs is still just a beginner.

Although, I (myself) have also been learning some things lately, with this subject matter, and I’m experiencing some lessons that make me realize I’m still ‘relatively’ a beginner – even after so many yrs So, if someone thinks I need to read a book or manual, just lemme know!

@Anthony_Yan

This XYZ-coordinate frame is known as the TNB frame. If you want more details about it, you can check Wikipedia or any textbook for vector calculus.

Perhaps I need to read a book on vector calculus

@Anthony_Yan

(3) Tapered threads are surprisingly subtle, in my opinion. I’m speaking as someone who tried to use Sweep1 and Sweep2 to create tapered threads. And then I wondered why my surfaces would not always stitch together into a watertight solid. Sometimes it did, and sometimes it didn’t. Turns out, mathematically it won’t stitch together, but if your tolerance is big enough, Rhino might let you get away with it. I’ll post more about this soon (later today or tomorrow). To understand this at a technical level, you need some vector calculus, namely the TNB frame. Sweep1 uses the TNB frame, so you need at least a conceptual understanding of it, to know why it fails only on tapered threads.

Idk bout vector calculus but it might just be a matter of how you setup your thread “cutting/forming” profile geometry?..

@Anthony_Yan

Why do I mention this? Because I’ve had the following experience: I’ve used sweep1 to create a thread along a helix. The threaded part is a single surface patch, which is supposed to have internal edges where a thread and the next turn of the thread seam together. In my experience, Rhino did not understand the internal edges, and Make Solid would fail.

I’ll be trying to see what you mean by this.

@Anthony_Yan

But a simple work-around was to cut the threads in half, by a plane that goes through the axis of the bolt. This slices the single-surface into many smaller surfaces (two patches per thread turn) that are individually simple. After that, Rhino would successfully Make Solid and stitch everything into a watertight solid.

It might just be a matter of how the threads are “cut/formed”. Indeed there’s many recipes for this and I’m not sure if GH makes it any easier, yet.